1. Field of the Invention
The present invention relates to the technology for storing the received response characteristics as well as the wireless technology utilizing the same, and it particularly relates to received response characteristics storing method and radio apparatus utilizing the same for determining the period during which the received response characteristics are retained.
2. Description of the Related Art
In wireless communication, it is generally desired that the limited frequency resources be used effectively. In an effective use of frequency resources, radio waves of the same frequencies are, for example, often used as repeatedly as possible in the short range. In such a case, however, communication quality deteriorates in the presence of cochannel interference from a nearby radio base station or wireless mobile station using the same frequency. One of the technologies for preventing the degradation of communication quality due to cochannel interferences is the adaptive array antenna technology.
Generally in the adaptive array antenna technology, signals received by a plurality of antennas are synthesized in the receiving processing by weighting them with their respective received weight vectors. Further, in the transmission processing, signals to be transmitted are separated by weighting them with transmission weight vectors and then transmitted from a plurality of antennas. In a series of processings, received weight vectors are estimated from a plurality of received signals and then transmission weight vectors are estimated from the received weight vectors, so that the received weight vectors estimated in the receiving processing are stored in a storing medium, such as a memory, until they are subjected to a transmission processing (see the Related Art List (1)).
Related Art List
(1) Japanese Patent Application Laid-Open No. 2000-332666.
Where a radio base station apparatus having adaptive array antennas is connected to a plurality of terminals by multiple access technology, such as TDMA (Time Division Multiple Access), it is sufficient to store applicable received weight vectors until a known transmission processing timing. On the other hand, where a radio base station is connected to a plurality of terminals by CSMA (Carrier Sense Multiple Access), the period of time during which the received weight vectors are to be stored is generally unknown because the transmission processing timing is unknown.